Thus, the problem posed is to provide PiP type coaxial pipes presenting thermal insulation in their annular space, which insulation is both effective in terms of the insulation it provides and is also simple to make and to put into place in the annular space between said pipe.
More particularly, the thermal insulation requirements of the present invention also include:                very high-performance insulation corresponding to values for the heat transfer coefficient of the order of a few milliwatts;        insulation that is compact so as to be capable of being received in small confined places (as required in the aerospace, aviation, and on-shore or off-shore oil industries);        thermal insulation that is light in weight so as to avoid disturbing and/or increasing the weight of the primary structure that is to be insulated (the insulation must not give rise to forces and stresses that are off specification);        thermal insulation that is easy to use and adaptable to all kinds of pipework; and        thermal insulation covering a wide range of temperatures from very low temperatures (−170° C. or less) up to high temperatures of the order of 150° C. to 200° C., or more.        